1. Field of the Invention
The present invention relates to an image forming apparatus that incorporates a belt unit including an endless belt.
2. Description of the Related Art
An electrophotographic image forming apparatus includes a transfer belt that transports a recording medium to a transfer point defined between a photoconductive drum and a transfer roller. A toner image is transferred from the photoconductive drum onto the recording medium. Electrical discharge occurs between the photoconductive drum and a recording medium during transfer of a toner image as well as separation of the recording medium from the photoconductive drum. For solving this problem, Japanese patent application No. 8-146781 employs a belt unit that incorporates a transfer belt having a value of ten-point height of roughness Rz greater than 4 μm may cause scattering of toner particles not only onto the recording medium but also onto the belt. For removing the toner from the belt, a cleaning blade made of a resilient material such as urethane rubber is used.
Recently, demand for high quality full color images printed by electrophotographic image forming apparatus is growing, expecting as good an image quality as silver halide photography. For achieving a high resolution image, use of spherical toner having a small diameter and a toner release agent such as wax has been proposed. However, when such a toner is used with a conventional image forming apparatus incorporating an endless belt having a value of ten-point height of roughness Rz greater than 4 μm, efficient cleaning of the endless belt over a long term is rather difficult. Deterioration of the cleaning performance leads to poor image quality.